php如何群发邮件

require 'PHPMailer/PHPMailerAutoload.php';

$mail = new PHPMailer;
$mail->isSMTP();
$mail->Host = 'smtp.example.com';
$mail->SMTPAuth = true;
$mail->Username = 'user@example.com';
$mail->Password = 'password';
$mail->SMTPSecure = 'tls';
$mail->Port = 587;

$mail->setFrom('from@example.com', 'From Name');
$mail->addAddress('to@example.com', 'To Name');
$mail->Subject = 'Email Subject';
$mail->Body = 'Email Body';

if (!$mail->send()) {
    echo 'Message could not be sent.';
    echo 'Mailer Error: ' . $mail->ErrorInfo;
} else {
    echo 'Message has been sent.';
}

require 'SwiftMailer/lib/swift_required.php';

$transport = (new Swift_SmtpTransport('smtp.example.com', 587))
    ->setUsername('user@example.com')
    ->setPassword('password');

$mailer = new Swift_Mailer($transport);

$message = (new Swift_Message('Email Subject'))
    ->setFrom('from@example.com', 'From Name')
    ->setTo('to@example.com', 'To Name')
    ->setBody('Email Body');

if (!$mailer->send($message)) {
    echo 'Message could not be sent.';
} else {
    echo 'Message has been sent.';
}